Cable telegraphy and the like



Sept. 11, 1928.

W. 8. SMITH ET AL CABLE TELEGRAPHY AND THE LIKE Filed Dec 27, 1927 Patented Sept. 11, 1928. lfigtiii UNITED STATES PATENT OFFHCE.

VJILLOUGHBY STATIIAM SMITH, BEE GT1- TON IP'OPPELFORD, AND NORMAN \VILLIAIVI MoLll. ENGLAND.

CABLE CZI Application filed December 132?. Serial No. 808, and in Great Britain August 23, 1926.

lhis invention relate to cable telen'raphy shunted by a condenser to reduce the efand the like. and especially to Cm feet of signal frequencies) to the cathode 9.

graph receivers employing; thermionic The capacity-shunted section 2 of the line valves. resistance is located at the cable end of the 5 The lnvention has for ob ect to provide resistance 8. and the grid and cathode of a 60 means for eliminating" or minimizing inter- 5 are directly connected ference due to ery 103V f qqiiejjcy CllSilli'bthGTG SCIOSS, ftl'lCl cathode Of a. 1'6- ances. especially slowly varying: earth curceivinp; valve 11 being connected respectiverents in a submarine cable telegraph sysly to a tapping point 12 which is preferably 59111 variaole as shown, upon the said resistance 65 In carrying out this invention an imped- 8, and to the earthed end of the line resistance comprising; two or more sections of suhmice 2. it is the receiving; device and 11 stantially different reactance is interposed the plate battery for the valve 11. Obviousin the common path of the signal currents ly any ampliiying' arrangement may be in- 15 and the low frequency disturbances. a tcrposed in iown manner between the valve 70 compensating thermionic valve or valves is 11 llil the receiver R.

or are associated. on the input side with Ii iGSilQCl a shaping: network may be of the said sections. and on the output side interposed between the line resistance 2 and with the thermionic valve receiver. whereby the Cable, and the compensating triode 5 a voltage change in the common path, due to nlfv be replaced by a plurality of triodes 75 a disturbance, is substantially compensated in parallel.

by a voltage cha e of opposite etieet ap It will be seen that a very low frequency plied to the thern onic receiver bv the comdisturbance will give rise to a voltage drop pensatingr thermionic valve or valves. across the capacity-shunted section 2 of the Preferably the impedance inserted in the line resistance, the said voltage drop giving 0 common path comprises two sections, one of rise to change of current in the anode cirwhich is substantially pure resistance, and cult of the compensating triode 5. Owing the other a capacitative resistant imto this chance of current there will be pedance of relatively high alternating curcaused a change of voltage drop across the i'ent resistance at disturbance frequency and resistance 8 in the said anode circuit, and 85 negligible alternating current resistance at therefore a change in the potential between signal frequency. grid and cathode of the thermionic receiver The invention is illustrated in the accom- 11, the last mentioned change serving to panyingr diagrammatic drawings, wherein: compensate for the change in the potential Figure 1 illustrates a receiving circuit arapplied by the disturbance directly to the 90 rangrz'emcnt embodying: the principles of our grid of the receiver valve. he compeninventi Fin. 2 shows a shaping network satin valve will, however, be substantially employed in the circuit arrangement of our una d by nals, owing to the action invention; and Fig. 3 shows a receiver cirof the shuntinn condenser, and to the choke 40 suit embodying the principles of our invGnin tl anode circuit of the said valve. 95 tion and compensated for voltage fluctual shaping network is employed, tions. i l. it ice and shunt capacity may,

Referring to ilwhich Shows One e; sired, form part thereof, additional inof carrying: out the invention, the cable 1 is and/or resistance and/or capacity connected to earth through line resistance connected in parallel with the said line 1 2, a section 2 of which, is shunted. by canee. Such arrangement is illuspacity 3 of such value that the impedance of igure 2, i hi h 13 14 are the 1 section and shunt capacity very low at signal frequency and high the a freque cy of disturbances such as slowly 8 and serving b0 reduce the effect of signal chan, earth currents. The grid 4.- of a l comp ensatinntriode 5 is connected to the .-.sired the primary of a transformer. cable 1, th 2 de circuit the s; 'd ed not t operate at frequencies b ingr completed through a choke 6, a; ode u those of the disturbances, may be battery 7 and a resistance 8 (which ma be connccte in the anode circuit of the com pensating triode, the secondary thereof being connected in the anode or the grid circuit c. This tinns'tormer serves to adjust for any over-com isetiou, due to high -tretpiency voltage Fluctuations. Such an arrungement is illustrated. in Figure 3, in which 10 is the trans'tormer serving to adjust for over-compensution. A high resistance may be shunted across the secondary of the trans't'ormer and/or a resistance may be associated with the primary thereof in order to adjust for amplitude and phase. It will be seen that any high frequency vol"- age fluctuations which may occur in the anode circuit of the valve 5 will cause the transformer 10 to apply a compensating potential to the grid of the said valve.

Obviously, the input to the compensating valve may it desired, he amplified by any suitable means, such a resistance coupled valve. Referrin to Figure 1, it a disturbance has arrived through the cable 1, then, owing to the tact that the impet cc of the section 2'3 (which is very low at signal frequency) is high a t disturbance "fretuiencies, there will be a voltage higher than that which would he set up by a signal. of corre sponding strength) generated across the said sect-ion 23. This voltage, applied between the grid and filan'i'ent oi the tube 5, will cuuse a variation in the plate current flowing in the plate circuit of this tube, and therefore a variation in the current flowing through the resistance 8.

Since the voltage across a resistance R,-

througzh which a current I flows, is given by the product there will obviously be a change in the voltage applied to the grid of the valve 11, said change of course serving to compensate for the change of voltage across the section 23, to which the change of voltage in the resistance 8 was due. This compensating cycle, as it may be termed, does not occur with signal voltages, since the impedance of the section 2'3 is low at signal frequencies.

While we have described our invention in certain preferred embodiments, we desire that it be understood that modifications may be made and that no limitations upon the invention are intended other than are imposed by the scope of the appended claims.

\Vhat we claim is 1. In a cable telegraph or the like receiver, the combination of an impedance located. in the common path of signal currents and low frequency disturbances, raid impedance com'- prisinga plurality of sections whose reatances at a given frequency are ditt'erent, and means for applying to a receiving device a compensating voltage change of. opposite etfect to a voltage change applied thereto by a disturbance, said means comprising thermionic means associated on the input side with one of said sections and on the output side with said receiving device.

2. In a cable teleoraph or the like receiver, the combination oi" an impedance located in the common path of signal currents and low frequency dist-url zinces, said imp-ecance comprising two sections constituted respectively by a resistance and a resistance shunted capacity, and means for applying; to a receiving device a compensating voltage cha' of opposite eliect to a voltage change applied thereto by a disturbance, said means comprising thermionic means associated on the input side with one of said sections and on the output side with said receiving; device.

3. In a cable telegraph or th lil: receiver, the combinetion of an impedance located in the common path of signal, currents and low frequency disturbanc aid impedance comprising two sections consth tuted respectively by a resistance and a resistance shunted capacity, and means for applying to a receiving;' device a compen eating voltage change of opposite el'lcct to a voltage change applied thereto by ta dis turbance, said means comprising a compensating; thermionic valve whose grid and cathode are connected across a capacity shunted resistance at the cable end of said impedance, the input terminals of said rcceiving device being connected between a point in the anode circuit oi said valve and the earth one of said impedance.

4. In av cable telegraph or the like receiver, the combination of an impedance located in the common path of signal currents and low frequency disturbances, said impedance comprising e. shaping network and a plurality of sections whose reactances at a given frequency are different, and means for applying to a receiving device a compensating voltage change of opposite etlect to a voltage change applied thereto by a disturbance, said means comprising thermionic means associated on tue input side with one of said sections and on the output .o with said receiving device.

5. In a cable telegraph or the like receiver, the combination of an impedance located in the common path of signal currents and low frequency di irbunces, said impedance comprising a shaping network and two sections con tituted respectively by a resistance and a ref ance shunted capacity, and menus or applying; to 2L receiving device a compensating voltage change of opposite effect to a voltage change applied thereto by a disturbance, said means comprising thermionic means associated on the input side ith one of sections and on the output side with said receiving device.

6. In a cable telv graph or the like r ceiver, the combination of an impedancelocated in the common path of signal cur rents and low frequency disturbances, said impedance comprising a shaping network and two sections constituteo respectively by a resistance and a resistance shunted capacity, and means for applying to a receiving device a compensating voltage change of opposite effect to a voltage change applied thereto by a disturbance, said means comprising a compensating thermionic valve whose grid and cathode are connected across a capacity shunted resistance at the cable end of said impedance, the input terminals of said receiving device being connected between a point in the anode circuit of said valve and the earth end of said impedance.

7. In a cable telegraph or the like receiver, the combination of an impedance located in the common path of signal currents and low frequency disturbances, said impedance comprising a plurality of sec tions whose reactances at a given frequency are different, means for applying to a receiving device a compensating voltage change of opposite effect to a voltage change applied thereto by a disturbance, said means comprising thermionic means associated on the input side with one of said sections and on the output side with said receiving device, and means for adjusting for over-compensation said last mentioned means, comprising a transformer inoperative at low or disturbance frequencies and operative at higl'ier frequencies associated with the output of said thermionic means and the input of said receiving device.

8. In a cable telegraph or the like receiver, the combination of an impedance located in the common path of signal currents and low frequency disturbances, said impedance comprising two sections constituted respectively by a resistance and a resistance shunted capacity, means for applying to a r ceiving device a compensating voltage change of opposite effect to a voltage change applied thereto by a disturbance,

said means comprising thermionic means associated on the input side with one of said sections and on the output side with said receiving device, and means for adjusting for over-compensation said last mentioned means, comprising transformer inoperative at low or disturbance frequencies and operative at higher frequencies associated with the output of said thermionic means and the input of said receiving device.

9. In a cable telegraph or the like receiver, the combination of an impedance located in the common path of signal currents and low frequency disturbances, said impedance comprising two sections constituted respectively by a resistance and a resistance shunted capacity, means for applying to a receiving device a compensating voltage change of opposite effect to a voltage change applied thereto by a disturbance, said means comprising a compensating therminoic valve whose grid and cathode are connected across a capacity shunted resistance at the cable end of said impedance, the input terminals of said receivingdevice bein connected between a point in the anodie circuit of said valve and the earth end of said impedance, and means for adjusting for over-compensation, said last mentioned means, comprising a transformer inoperative at low or disturbance frequencies and operative at higher frequencies associated with the output of said thermionic means and the input of said receiving device.

10. In a cable telegraph or the like receiver, the combination of an impedance located in the common path of signal currents and low frequency disturbances, said impedance comprising a shaping network anda plurality of sections whose reactances at a given frequency are different, means for applying to a receiving device a compensating voltage change of opposite effect toa voltage change applied thereto by a disturbance, said means comprising thermionic means associated on the input side with one of said sections and on the output side with said receiving device, and means for adjusting for over-compensation said last mentioned means, comprising a ransformer inoperative at low or disturbance frequencies and operative at higher frequencies associated with the output of said thermionic means and the input of said receiving device,

11. In a cable telegraph or the like receiver, the combination of an impedance located in the common path of signal currents and low frequency disturbances, said impedance comprising a shaping network and two sections constituted respectively by a resistance and a resistance shunted capacity, means for applying to a receiving device a compensating voltage change of opposite effect to a voltage change applied thereto by a disturbance, said means comprising thermionic means associated on the input side with one of said sections and on the output side with said receiving device, and means for adjusting for over-compensation said last mentioned means, comprising a transformer inoperative at low or disturbance frequencies and operative at higher frequencies associated with the output of said thermionic means and the input of said receivin device.

12. In a cable telegraph or the like receiver, the combination of an impedance located in the common path of signal currents and low frequency disturbances, said impedance comprising a shaping network and two sections constituted respectively by a resistance and a resistance shunted capacity, means for applying to a receiving de vice a compensating voltage change of opposite effect to a voltage change applied thereto by a disturbance, said means comprising a compensating thermionic valve whose grid and cathode are connected across a capacity shunted resistance at the cable end of said impedance, the input terminals of said receiving device being connected between a point in the anode circuit of said *alve and the earth end of said impedance, and means for ad ustmg for over-compensation said last mentioned means, comprising a transformer associated with the 1 output of said thermionic means and the input of said receiving device.

In testimony that We claim the foregoing as our invention We have signed our names this ninth day of December 1927.

WILLOUGHBY STATHAM SMETH. NORMAN WILLIAM McLACHLAN. 

